The present invention relates to a novel flux compression generator suitable for achieving high velocity firing of projectiles.
Presently, there is a need to extend the range of, for example, 155 mm Cannons and 120 mm Mortars far beyond the current state-of-the-art ranges of 45 kilometers for artillery and 10 kilometers for mortars.
Traditionally, projectile muzzle velocity was achieved using the energy associated with the propellants acting on the projectile along the barrel length. [Army (February 1965), Interior Ballistics of Guns, Engineering Design Handbook: Ballistics Series, United States Army Materiel Command, AMCP 706-150]. Final velocity was limited by projectile mass, barrel length, propellant mass, and the ability of the breech and barrel to withstand internal pressure from propellant combustion. Further, muzzle velocity is limited by the sound speed of the propellant gases providing projectile acceleration. [Wikipedia.org/wiki/light_gas_gun: Light Gas Gun: Design Physics, 2013.]. Thus, regardless of the amount of propellant used, barrel strength or length, or diminishing projectile mass, projectile velocity exiting the muzzle is limited. With this limitation, a gun design efficiency diminishes correspondingly as the theoretical limit is approached, i.e., progressively more propellant energy is wasted.
For service use, generally, gun and mortar design utilize a range of aforementioned parameters to produce relatively low performance but efficient systems. As the demand for higher projectile velocity has increased to obtain greater range or improved hit probability for fast maneuvering targets, designs have moved toward higher muzzle velocity at the expense of efficiency. Some of the efficiency has been recouped through research providing more energetic propellants and igniters, and improved gun barrel materials, for example.
Higher projectile velocity providing extended range for artillery fire has been successfully achieved using rocket-assisted projectiles RAP. [General Dynamics Ordnance and Tactical Systems, 155MM M549A1 HE-RAP, www.gd-ots.com, 2013]. In these systems, payload is comprised of the projectile to be delivered on target plus the additional mass of the rocket. As such, only a relatively small projectile can be propelled to extended range. Further, cartridge case design is complex requiring additional igniters and timing mechanisms for the rocket portion of the payload. In addition, these systems are very inefficient in terms of the total propellant expended to achieve a given projectile velocity.
Research over the past twenty years or so has developed the possibility of electromagnetic launch of projectiles at hypersonic velocity using “rail gun” techniques. [Sofge, Erik (Nov. 14, 2007). “World's Most Powerful Rail Gun Delivered to Navy”. Popular Mechanics, 2007]. As such, projectile velocity is not limited by conventional propellant sound speeds. While very high projectile velocities can be achieved, the launch systems generally are massive, and the launch phase has been plagued with electromagnetic erosion of sliding contacts and sabot materials that support the projectile during launch. In order to survive, the sliding contacts moving with the projectile have to be relatively massive, thus the projectile mass necessarily must be small to achieve hypersonic velocity. Further, the system requires a massive external generator such as a holopolar generator with magnetic braking, for example, as a power source. Also, the rail launch technique requires a completely new gun system and does not lend itself to integration into an existing howitzer or artillery cannons.
An additional approach has been a two-stage gun wherein the first stage is driven by conventional propellant while second stage is filled with light gas like helium that has higher sound velocity. [Wikipedia, supra]. Action of the propellant gases on an intervening diaphragm creates rupture that allows energy to compress the light gas with resulting force placed on the projectile base as it travels down the second stage barrel. With this system, projectile final velocity remains limited, but at a higher level. Such an approach increases the barrel length substantially and requires an external source of helium to recharge the second stage after each launch. This system is more massive and increases time interval between firings.
Projectile acceleration by a coil gun using single or multiple coils has been examined mainly to produce gun systems that do not rely on propellants. [Army Times: EM technology could revolutionize the mortar, 2011]. These systems also are not limited by propellant sound speeds. The power source is external and massive while fast acting and relatively massive switching devices are required. The more efficient higher performing coil guns contain multiple coils that require additional fast acting switches as the projectile passes from one coil to another. An advantage over rail gun is that little friction, if any, is present between the coil and projectile unlike the sliding contacts used in the rail gun launch technique. Power systems generally require a fast acting external homopolar generators or large capacitor banks.
Taking into account the complexities related to existing approaches for projectile launch at high velocity, the present invention overcomes many of these drawbacks. A direct application to gun and mortar systems is possible without modification to the gun structure supporting the gun breech and barrel or the gun breech itself. Modification to the barrel would be required. Otherwise the invention redistributes propellant energy loaded normally in the breech into electromagnetic energy for projectile acceleration to high velocity. Therefore, the invention has advantages in terms of utility, costs, simplicity and performance.